1. Field of the Invention
The present invention relates to a lens array sheet, a light source and a liquid crystal display device.
2. Description of the Related Art
Recently, a liquid crystal panel such as liquid crystal display device has been gradually enlarged. Although the liquid crystal panel may be enlarged, it is not allowed to degrade the image quality of the panel and it is demanded that high definition image quality of the panel can be achieved even for a large-scale screen. In order to achieve the high definition image quality for the large-scale screen, for example, it is strongly demanded that brightness of the screen can be maintained or improved, or viewing angle can be widened. In accordance with these demands, some techniques have been proposed to arrange a micro array lens in the liquid crystal panel and improve the brightness and the viewing angle of the liquid crystal panel. Arranging the micro array lens makes it possible to enhance front face brightness and/or widen the viewing angle.
On the contrary, there is an issue to be solved, because moire fringes may appear and visibility may become lower due to the fact that the liquid crystal panel includes an array of regular pixels (i.e., picture elements). The moire fringes are a fringe pattern which is produced by overlapping a plurality of regular repetitive patterns and visually observed by a deviation of periods between the plurality of regular repetitive patterns. The moire fringes in the liquid crystal panel are produced as each pixel in the liquid crystal panel forms a regular repetitive pattern and other members and the like has a similar regular repetitive structure.
Japanese Patent Application Laid-Open No. 2000-206529 discloses moire fringes as mentioned above and a method of reducing such moire fringes.
An optical sheet having a structured pattern of a regular pitch may be used as a launching member for guiding light from a backlight to a liquid crystal panel. In this case, overlapping of pixels forming the regular pitch of the liquid crystal panel and the structured pattern of the optical sheet overlaps light and dark lattices and causes moire fringes to be produced. A liquid crystal display device disclosed in JP-A No. 2000-206529 is arranged to reduce the moire fringes by configuring an array pitch of pixels and the pitch of the structured pattern of the optical sheet so as to minimize a pitch distance of the moire fringes. In other words, the liquid crystal display device is arranged to reduce effects of the moire fringes on the image quality by minimizing the pitch distance of the moire fringes and thus decreasing the pitch distance to a level not more than resolution of human eye.